Extract from Why Gardens Matter by Joanna Geyer-Kordesch

18 why gardens matter
effective, when and how to apply it, were highly valued and this
knowledge built on the tradition of Herbals.
Dioscorides, in his famous De Materia Medica, developed
the Herbal in manuscript form that everyone referred to and used
for centuries beyond its inception, around 500 ad. Later Herbals
also included plants from further north with descriptions of new
plants that were encountered in specific regions. It was practical
to have plants specified in the medical sense, but also described
for their own sake. Alas, the Herbals and their illustrations did
not distinguish old from new. The theoretical knowledge of
plants was there, but usage was increasingly dependent on being
familiar with what actually grew in the ground.
By medieval times, salvation of the physical body, as well
as of the soul, was in the hands of learned monks and abbots,
who advanced their knowledge in special gardens near their infirmaries.
Monks increasingly lived many tiered working lives,
centred on communal prayer and private silence, but practising
advanced study, horticulture, open hospitality and care for the
ill. Those who could read did so in several languages, especially
Latin. Herbals were often in this tongue as well as later in the
vernacular. They had plant descriptions in words and pictures,
but these were often stylised. You had to know the herbs in practice
alongside the description in the book or manuscript, as there
was always the danger of applying the wrong plant or the wrong
dosage.
As the manuscripts were converted to printed books, after
1470, plants were valued more and more for their specific characteristics
in their locality and were recorded in this way for publication.
The plants whose features were delineated became objects
whose natural qualities were worthy of study in their own
right. In a sense the written and printed Herbals were the first
books to demand that plants be characterised apart from their
medicinal use. In this way medicine helped evolve the description
and classification of plants into taxonomy and botany.